1. Field of the Invention
This invention relates to mesoionic 1,2,4-triazolium-3-thiolate silver halide stabilizer precursors and the use of such precursors in heat developable and heat stabilizable photographic silver halide materials and processes. It also relates to use of such stabilizer precursors in photographic silver halide processing compositions.
2. Description of the State of the Art
Mesoionic sulfur-containing tetrazole compounds have been described in the photographic art as photographic additives in, for instance, U.S. Pat. No. 4,003,910. These compounds are not described as useful in a heat developable and heat stabilizable photographic material and process.
The use of stabilizer precursors in heat developable and heat stabilizable photographic materials and processes is known. Examples of known stabilizer precursors are described in, for instance, U.S. Pat. No. 4,012,260. An example of a heterocyclic stabilizer precursor is 2-amino-2-thiazolinium trichloroacetate.
A related heat developable and heat stabilizable photographic silver halide material comprising photographic silver halide, a photographic silver halide developing agent, an activating concentration of a thermal base releasing compound, and a stabilizing concentration of a mesoionic 1,2,4-triazolium-3-thiolate silver halide stabilizer is described in copending U.S. Application Ser. No. 215,786 of H. W. Altland, E. L. Dedio and G. J. McSweeney, filed Dec. 12, 1980, 1980, entitled "Mesoionic Silver Halide Stabilizer in a Heat Developable and Heat Stabilizable Photographic Silver Halide Material and Process". A problem exists with such materials containing a stabilizer in that the stabilizer can cause undesired sensitometric changes in the photographic silver halide prior to exposure and processing. No suitable answer to this problem is found in the copending application or in the above patents.
A continuing need has existed for stabilizers that provide water-soluble light-insensitive silver (I) complexes upon exposure and heating of a heat developable and heat stabilizable photographic silver halide material. Such water-soluble light-insensitive silver (I) complexes help provide light stability to a developed image in a processed photographic silver halide element.
The term "material" as used herein, such as in "photographic silver halide material", refers to photographic elements and photographic compositions. For instance, the term "heat developable and heat stabilizable photographic silver halide material" refers to photographic elements and photographic compositions that are heat developable and heat stabilizable.